Solid state elapsed time indicators have been available for some time to indicate aggregate running time. However, they have not been readily adopted by the general public due to various inefficiencies which have plagued these types of indicators, usually related to their inordinate cost, their size, as well as unusual sensitivity to vibration. The verge mechanism which has typically been employed in such indicators, has suffered from the inability to maintain close dimensional tolerances rendering the indicator unreliable over long periods of time. Also, there is substantial electrical sensitivity to voltage and temperature variations, and poor resistance to voltage transients and spikes on the input power lines and susceptibility to radiated noise.
It is an object of the invention described herein to overcome many of the problems which have plagued solid state elapsed time indicators as explained above and to make them more efficient, more accurate and less costly so that they may be more readily accepted by the general public.
It is another object to use a drive mechanism which reduces the drive torque required to create a corresponding reduction in the electromagnet size needed to operate the drive mechanism.
It is further object of the invention to provide an inverse escapement mechanism for acting on drive wheel teeth which is much less sensitive to dimensional changes due to wear, temperature and manufacturing tolerances than verge mechanisms which have existed heretofore.
It is still another object to arrive at a design for fixing the various elements comprising the elapsed time indicator together within a housing at minimal effort to reduce cost while increasing the efficiency of operation of the indicator.
Another object of the invention is to provide an improved verge escapement mechanism in which a verge member is driven by an electromagnet under the control of a solid state time base and driver circuit.
It is another object of the invention to employ unique core frame assembly with the electromagnet to readily and quickly place the electromagnet in the proper position relative to the verge member without relying on air gap adjustments and other assembly tasks which have been required before.
These and other objects will become more apparent from the detailed description of the preferred embodiment and the claims which follow hereinafter.